Recent advances in the fabrication of ultratransparent materials have demonstrated that fibers are a promising transmission medium for optical communication systems. These light transmitting fibers, which are referred to as optical waveguides, generally consist of a transparent core surrounded by a layer of transparent cladding material having a refractive index which is lower than that of the core. A low loss optical waveguide and a method of making the same are disclosed in U.S. Pat. No. 3,659,915. The waveguide described in that patent comprises a cladding layer of fused silica and a core of fused silica doped with one or more materials that selectively increase the refractive index of the core above that of the cladding.
To provide redundancy in the case of fiber breakage and/or to provide for the simultaneous transmission of a plurality of optical signals, such fibers are usually grouped together in bundles or ribbons. However, if such fibers are to be readily used in this manner, it is evident that there must be a quick, convenient and accurate means of connecting sections of fibers together in the course of their use. Devices for connecting ribbons and bundles of optical fibers are respectively disclosed in U.S. Pat. No. 3,864,018 issued to C. A. Miller and U.S. patent application Ser. No. 498,329 entitled "Optical Waveguide Connector" filed Aug. 19, 1974 by R. M. Hawk. Both of these connectors require that the optical fibers be disposed in linear arrays, the fiber endfaces being substantially perpendicular to the fiber axes and being substantially coplanar. Thus, when the fibers from each bundle or ribbon are disposed in the connector, all of the corresponding pairs of fibers to be connected are in virtual contact. If the endfaces of each fiber array are not coplanar, end separation will occur between some of the fiber pairs to be connected, resulting in an additional loss at that junction.
A method for preparing the end of a single optical fiber such that the endface thereof is substantially flat and perpendicular to the axis thereof is disclosed by D. Gloge et al. in their publication entitled "Optical Fiber End Preparation for Low-Loss Splices," Bell System Technical Journal, Vol. 52, November, 1973, pp. 1579-1588. This publication discloses a reliable method of breaking an optical fiber to obtain a flat, perpendicular endface by controlling the stress distribution in the fracture zone of the fiber. Depending upon the Young's modulus of the fiber material and the diameter of the fiber, the fiber is bent to the required radius and is subjected to the required tension for achieving the aforementioned stress distribution therein. By lightly scoring the fiber periphery, a break is initiated and propagates through the fiber to provide an optically smooth endface.
The apparatus disclosed in the aforementioned Gloge et al. publication employs two non-slip fiber clamps, one of which is mounted on a spring steel bar. The fiber is slidably retained by a fiber guide and passes over a curved form. By raising the form the displacement of the fiber from its original linear disposition puts the fiber into a state of tension, the extent of which can be measured by a tension guage which measures the mechanical displacement of the steel bar. If a plurality of fibers were clamped into this apparatus and the tension increased in accordance with the number of fibers, the tension on each fiber would not necessarily be equal. Furthermore, after one fiber became severed, the tension on each of the remaining fibers would increase. To provide each fiber with its own tension applying clamp and tension gauge would result in an apparatus so unwieldy as to be useless for field use.